Telephone system



Sept. 1 2, 1939. v A, R K 2,172,874

TELEPHONE SYSTEM Filed Dec. 16, 1936 I RING-[ENE tm I Ell m Patented Sept. 12, 1939 UNITED STATES TELEPHONE SYSTEM Arthur Robert Kahl, Coventry, England, assignor to The General Electric Company Limited,

Coventry, England Application December 16, 1936, Serial No. 116,071 In Great Britain January 23, 1936 3 Claims.

The present invention relates to telephone systems, and has for its object the provision of means whereby a reply to a call made by a subscriber to an operator or other callable station, is not unduly delayed.

In automatic telephone systems, it is common practice for the subscriber to dial the digit to obtain the services of an operator, this class of call being also used in any case of emergency.

As, however, the number of operators available at night is usually limited, it might easily happen that such a call remained unanswered for a considerable length of time. This should be avoided as some of the calls are of extreme urgency, such as fire, police and the like.

According to the invention a call made to an operator through an automatic exchange by the sending of a calling signal such as the digit 0, is connected to means whereby an urgent alarm is given or a particular station is signalled if the call is not answered within a predetermined time and/or if the caller sends further impulses or signals without first normalising the apparatus in the circuit.

In one embodiment of the invention the single digit 0 is chosen for the purpose of calling the operator on account of its common usage by subscribers and simplicity of signalling in the darkness. The normal 0 level circuit, by which the operator-directed call reaches the manual board, is amended by the provision of an impulse responding device such as a step-by-step switch and associated relay group, and also further means such as connection to a time delay circuit.

The time delay circuit and the impulse responding circuit are connected to an alarn relay individual to the 0 level circuit, this relay being operated either at the end of the predetermined time after the particular circuit has been taken into use or by the sending of a further signal or signals by the subscriber.

When the said alarm relay operates, the seized 0 level circuit is connected to a multiple of urgent jacks suitably disposed around the switchboard and in addition urgent visual or audible alarms may be given.

In an alternative form of circuit, means are provided in common to a group of 0 level circuits, seizure of one of the said circuits causin the selection of a digit sending apparatus which may comprise step-by-step switches, and relay groups, the said apparatus being adapted to route the call to a specific destination such as a police station.

Turning now to the accompanying drawing which shows a circuit according to the invention, it will be seen that of the lines I, 2 and 3 connected to the negative, positive and private banks respectively of exchange selectors, two ter- 5 minate on a relay A which provides battery supply to the subscriber. When the latter dials a predetermined digit such as 0, his line is extended by the first selector or similar switch to the leads I, 2 and 3, and relay A operates. So far, the practice is similar to standard as regards 0 level calls. Relay A initiates the following functions:

al operates relay B.

a2 prepares a loop for signalling to the operators cord circuit later.

bl applies ringing tone to lead I and hence to the subscribers instrument.

b2 applies earth potential to lead 3 thus engaging the outlet to other selectors.

b3 operates relay TA on one coil in series with TM but the latter, being insensitive, does not itself operate, as the operating coil of relay TA is of high resistance.

b4 prepares to operate relay TO.

b5 prepares a stepping path for the driving magnet DM.

b6 lights the calling lamp CL to attract the attention of the operator.

bl prepares a locking path for relay TO.

ml connects impulse cam K to the magnet UM of a step by step switch U which is common to a number of 0 level circuits. This switch now proceeds to step at a slow rate. If the operator replies at once or after a short period, relay S is operated by the insertion of the plug in the jack AJ, this relay performing the following functions:

sl extinguishes the calling lamp CL. 82 removes ring tone from the subscribers line. s3 releases relay TA.

s4 prevents additional impulsing of relay A from stepping switch D. The operator can now attend to the requireis delayed and the subscriber dials any further digit other than 1, contact al impulses the driving magnet DM Via contact b5.

Wiper D2 now steps on to contacts connected to earth, this potential operating relay TO via contact M. The relay locks itself operated through its own contact 1505 to contact bl, the remaining contacts performing the following functions:

tol and 2502 connect the leads I and 2 to an urgent jack UJ on another operators position which is always attended.

to3 lights a calling lamp UL associated with the jack UJ.

1504 brings into operation a bell UB which gives an audible signal.

toE extinguishes the lamp CL on the position on which the call first appeared.

When the operator attends to the urgent call by plugging into the jack UJ, relay SA operates.

sci extinguishes the lamp UL.

sa'? silences the bell UB.

sat removes ringing tone from lead I. saireleases relay TA.

The call is now attended to, at the end of which relays A and B release when the subscriber replaces the receiver. The switch D is now stepped to a normal position by earth potential derived from Di via the self-interrupter contacts dm and contact 125.

Should the caller refrain from dialling an extra digit, then a further action takes place. The switch U continues to be impulsed as previously described, until the wiper Ul encounters the second contact on its bank. In this position a second low resistance winding of relay TA is placed in parallel with the first winding, and the relay, whilst remaining held operated, allows sufficient current to pass through it to operate TM, which looks in this position at its contact tml. The switch continues to step until its wiper U2 finally encounters the first contact in its bank after a delay determined by the number of contacts per bank and the rate of stepping derived from the cam K. When it reaches the point stated, earth from Wiper U2 is applied through contact tm2 to one coil of relay TO, which operates and locks itself in this position to contact bl. The contacts of this relay perform functions similar to those already described and the call is transformed from a normal 0 level call into an urgent one. All subsequent operations are similar to those described for the case in which the subscriber dials an extra digit.

Although the invention has been described as utilizing only one "urgent jack p'er exchange, it is obviously not limited thereto. Methods are well known in the art whereby urgent calls maturing simultaneously could be arranged to appear singly on a plurality of jacks, or could utilize the same urgent jack in succession.

Similarly although the urgent calls are described as appearing on a jack attended by an operator, they could alternatively be connected directly to a line to, for example, a police or fire station, this being accomplished by means of a common impulse-sending apparatus comprising a step-by-step switch or switches and a control group of relays. Such devices are known in the art, and could easily be adapted to perform the functions required. Thus when an 0 level call became urgent, the procedure would be for the affected 0 level circuit to seize the impulse sending device which would then connect the call to normal exchange apparatus and set the latter on a predetermined number.

I claim:

1. In a telephone system, an operators trunk circuit terminating in jacks, a signal for each jack, subscribers lines, means controlled over a subscribers line for extending a call to said trunk circuit and always operating the signal associated with one of said jacks, and means responsive to the transmission of further impulses to the trunk circuit by the subscriber after the trunk is seized for operating the second signal associated with another jack.

2. In a telephone system, an operators position terminating in the answering jacks, calling lines, means controlled from a calling line for extending a call to the position and operating a signal associated with one of said jacks, an urgent signal associated with another jack, a relay at the position, a step-by-step switch, said relay responsive to a series of impulses over a calling line after the said first signal is operated for operating said switch to cause operation of the urgent signal.

3. In a telephone system, trunk circuits extending to an operators position, calling lines, means for completing calls for calling lines to said trunk circuits and signalling the operator thereat, a special operators trunk and signal, a timing switch for switching a call to said special trunk a predetermined time after the call is extended thereto if the call on the trunk circuit is not answered, and another switch controlled by the calling subscriber for promptly operating the signal at the special trunk in case of urgent calls.

' ARTHUR ROBERT KAHL. 

